[Qemu-devel] [PATCH v2 2/6] block: vmdk - move string allocations from stack to the heap

[Jeff Cody]

Functions 'vmdk_parse_extents' and 'vmdk_create' allocate several
PATH_MAX sized arrays on the stack.  Make these dynamically allocated.

Signed-off-by: Jeff Cody <address@hidden>
---
 block/vmdk.c | 64 ++++++++++++++++++++++++++++++++++++------------------------
 1 file changed, 38 insertions(+), 26 deletions(-)

diff --git a/block/vmdk.c b/block/vmdk.c
index dc6459c..043a750 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -784,7 +784,7 @@ static int vmdk_open_sparse(BlockDriverState *bs,
 static int vmdk_parse_extents(const char *desc, BlockDriverState *bs,
                               const char *desc_file_path, Error **errp)
 {
-    int ret;
+    int ret = 0;
     int matches;
     char access[11];
     char type[11];
@@ -792,12 +792,11 @@ static int vmdk_parse_extents(const char *desc, 
BlockDriverState *bs,
     const char *p = desc;
     int64_t sectors = 0;
     int64_t flat_offset;
-    char extent_path[PATH_MAX];
+    char *extent_path = g_malloc0(PATH_MAX);
     BlockDriverState *extent_file;
     BDRVVmdkState *s = bs->opaque;
     VmdkExtent *extent;
 
-
     while (*p) {
         /* parse extent line in one of below formats:
          *
@@ -814,18 +813,21 @@ static int vmdk_parse_extents(const char *desc, 
BlockDriverState *bs,
         } else if (!strcmp(type, "FLAT")) {
             if (matches != 5 || flat_offset < 0) {
                 error_setg(errp, "Invalid extent lines: \n%s", p);
-                return -EINVAL;
+                ret = -EINVAL;
+                goto exit;
             }
         } else if (!strcmp(type, "VMFS")) {
             if (matches == 4) {
                 flat_offset = 0;
             } else {
                 error_setg(errp, "Invalid extent lines:\n%s", p);
-                return -EINVAL;
+                ret = -EINVAL;
+                goto exit;
             }
         } else if (matches != 4) {
             error_setg(errp, "Invalid extent lines:\n%s", p);
-            return -EINVAL;
+            ret = -EINVAL;
+            goto exit;
         }
 
         if (sectors <= 0 ||
@@ -840,7 +842,8 @@ static int vmdk_parse_extents(const char *desc, 
BlockDriverState *bs,
         {
             error_setg(errp, "Cannot use relative extent paths with VMDK "
                        "descriptor file '%s'", bs->file->filename);
-            return -EINVAL;
+            ret = -EINVAL;
+            goto exit;
         }
 
         path_combine(extent_path, sizeof(extent_path),
@@ -849,7 +852,7 @@ static int vmdk_parse_extents(const char *desc, 
BlockDriverState *bs,
         ret = bdrv_open(&extent_file, extent_path, NULL, NULL,
                         bs->open_flags | BDRV_O_PROTOCOL, NULL, errp);
         if (ret) {
-            return ret;
+            goto exit;
         }
 
         /* save to extents array */
@@ -860,7 +863,7 @@ static int vmdk_parse_extents(const char *desc, 
BlockDriverState *bs,
                             0, 0, 0, 0, 0, &extent, errp);
             if (ret < 0) {
                 bdrv_unref(extent_file);
-                return ret;
+                goto exit;
             }
             extent->flat_start_offset = flat_offset << 9;
         } else if (!strcmp(type, "SPARSE") || !strcmp(type, "VMFSSPARSE")) {
@@ -874,13 +877,14 @@ static int vmdk_parse_extents(const char *desc, 
BlockDriverState *bs,
             g_free(buf);
             if (ret) {
                 bdrv_unref(extent_file);
-                return ret;
+                goto exit;
             }
             extent = &s->extents[s->num_extents - 1];
         } else {
             error_setg(errp, "Unsupported extent type '%s'", type);
             bdrv_unref(extent_file);
-            return -ENOTSUP;
+            ret = -ENOTSUP;
+            goto exit;
         }
         extent->type = g_strdup(type);
 next_line:
@@ -893,7 +897,9 @@ next_line:
             p++;
         }
     }
-    return 0;
+exit:
+    g_free(extent_path);
+    return ret;
 }
 
 static int vmdk_open_desc_file(BlockDriverState *bs, int flags, char *buf,
@@ -1797,10 +1803,15 @@ static int vmdk_create(const char *filename, QemuOpts 
*opts, Error **errp)
     int ret = 0;
     bool flat, split, compress;
     GString *ext_desc_lines;
-    char path[PATH_MAX], prefix[PATH_MAX], postfix[PATH_MAX];
+    char *path = g_malloc0(PATH_MAX);
+    char *prefix = g_malloc0(PATH_MAX);
+    char *postfix = g_malloc0(PATH_MAX);
+    char *desc_line = g_malloc0(BUF_SIZE);
+    char *ext_filename = g_malloc0(PATH_MAX);
+    char *desc_filename = g_malloc0(PATH_MAX);
     const int64_t split_size = 0x80000000;  /* VMDK has constant split size */
     const char *desc_extent_line;
-    char parent_desc_line[BUF_SIZE] = "";
+    char *parent_desc_line = g_malloc0(BUF_SIZE);
     uint32_t parent_cid = 0xffffffff;
     uint32_t number_heads = 16;
     bool zeroed_grain = false;
@@ -1916,33 +1927,27 @@ static int vmdk_create(const char *filename, QemuOpts 
*opts, Error **errp)
         }
         parent_cid = vmdk_read_cid(bs, 0);
         bdrv_unref(bs);
-        snprintf(parent_desc_line, sizeof(parent_desc_line),
+        snprintf(parent_desc_line, BUF_SIZE,
                 "parentFileNameHint=\"%s\"", backing_file);
     }
 
     /* Create extents */
     filesize = total_size;
     while (filesize > 0) {
-        char desc_line[BUF_SIZE];
-        char ext_filename[PATH_MAX];
-        char desc_filename[PATH_MAX];
         int64_t size = filesize;
 
         if (split && size > split_size) {
             size = split_size;
         }
         if (split) {
-            snprintf(desc_filename, sizeof(desc_filename), "%s-%c%03d%s",
+            snprintf(desc_filename, PATH_MAX, "%s-%c%03d%s",
                     prefix, flat ? 'f' : 's', ++idx, postfix);
         } else if (flat) {
-            snprintf(desc_filename, sizeof(desc_filename), "%s-flat%s",
-                    prefix, postfix);
+            snprintf(desc_filename, PATH_MAX, "%s-flat%s", prefix, postfix);
         } else {
-            snprintf(desc_filename, sizeof(desc_filename), "%s%s",
-                    prefix, postfix);
+            snprintf(desc_filename, PATH_MAX, "%s%s", prefix, postfix);
         }
-        snprintf(ext_filename, sizeof(ext_filename), "%s%s",
-                path, desc_filename);
+        snprintf(ext_filename, PATH_MAX, "%s%s", path, desc_filename);
 
         if (vmdk_create_extent(ext_filename, size,
                                flat, compress, zeroed_grain, opts, errp)) {
@@ -1952,7 +1957,7 @@ static int vmdk_create(const char *filename, QemuOpts 
*opts, Error **errp)
         filesize -= size;
 
         /* Format description line */
-        snprintf(desc_line, sizeof(desc_line),
+        snprintf(desc_line, BUF_SIZE,
                     desc_extent_line, size / BDRV_SECTOR_SIZE, desc_filename);
         g_string_append(ext_desc_lines, desc_line);
     }
@@ -2007,6 +2012,13 @@ exit:
     g_free(backing_file);
     g_free(fmt);
     g_free(desc);
+    g_free(path);
+    g_free(prefix);
+    g_free(postfix);
+    g_free(desc_line);
+    g_free(ext_filename);
+    g_free(desc_filename);
+    g_free(parent_desc_line);
     g_string_free(ext_desc_lines, true);
     return ret;
 }
-- 
1.9.3